Zoonotic risk of transmission of Giardia duodenalis from water resources; Worldwide molecular and network analyses.

Giardia duodenalis, is an intestinal protozoon, the significant cause of waterborne outbreaks in the world. Eight known assemblages (A-H) have been reported in G. duodenalis, of which the assemblages A and B are frequently reported in humans. This study aims to compare the diversity haplotypes and genetic differences between the assemblages A and B of G. duodenalis in surface water, based on the triosephosphate isomerase (TPI), beta-giardin (BG), and glutamate dehydrogenase (GDH) genes. Sequences up to June 2024 for the TPI (104-61), BG (78-87), and GDH (105-64) genes, pertaining to assemblages A and B, were retrieved from the GenBank. A comprehensive molecular analyses were performed using DnaSP and PopART software. In addition, gene flow analysis for the sequences regarding the continents was performed. Molecular analysis showed higher number of haplotypes in the assemblage A compared to the assemblage B for all genes. Except for the gene TPI, the haplotype diversity (Hd) in assemblage B was higher than assemblage A. The Tajima's D and Fu values were negative for all genes in both assemblages A and B, while they were significant in all samples except for the genes GDH and BG in assemblage B. The lack of clear knowledge about the ecology and epidemiology of G. duodenalis makes it difficult to draw definitive conclusions about the transmission dynamics of G. duodenalis. However, the current genetic analyses of common assemblages can provide a clue about the risk of transmission of G. duodenalis from water resources.